This book contains selected papers from the KES-IDT-2021 conference, being held as a virtual conference in June 14–16, 2021. The KES-IDT is an interdisciplinary conference with opportunities for the presentation of new research results and discussion about them under the common title "Intelligent Decision Technologies". The conference has been creating for years a platform for knowledge transfer and the generation of new ideas in the field of intelligent decision making. The range of topics discussed during the conference covered methods of classification, prediction, data analysis, big data, decision support, knowledge engineering, modeling, social networks and many more in areas such as finance, economy, management and transportation. The discussed topics covered also decision making for problems regarding the electric vehicle industry. The book contains also several sections devoted to specific topics, such asAdvances in intelligent data processing and its applicationsMulti-criteria decision analysis methodsKnowledge engineering in large-scale systemsHigh-dimensional data analysisSpatial data analysis and sparse estimationInnovative technologies and applications in computer intelligenceIntelligent diagnosis and monitoring of systemsDecision making theory for economics.